One of the most common causes of electrical circuit or system failure is a short circuit. Shorts occur due to a variety of causes, including electrical component failure, damaged wiring, or damaged insulation. To restore the shorted electrical circuit to normal operation, the short must be located and the failed component, wiring, or insulation replaced. Precisely identifying the location and cause of a short circuit, however, is frequently a difficult and time-consuming task.
The challenge of locating shorts is one commonly faced by home appliance and HVAC service technicians. To verify the existence of a short, the service technician may replace a blown fuse with another fuse, or manually reset a tripped circuit breaker. However, if the short is drawing sufficient current, this will only result in another blown fuse or tripped circuit breaker, and the technician will not be aided in pinpointing the exact location of the short. In order to overcome these limitations, many service technicians jump the terminals of a blown fuse or tripped circuit breaker, and thereafter move wires around or probe different points in the local circuit in an effort to pinpoint the location of the short. Unfortunately, in the meantime, the appliance or HVAC transformer and other circuit components may overheat and become damaged.
Short locating tools are well known. For example, U.S. Pat. No. 4,353,026 to Edwards, Jr., discloses a short locating tool for high voltage applications utilizing two momentary push buttons, a relay circuit, and an audible horn that emits an audible alarm when a short is cleared. The short locating tool does not, however, include any short-circuit protection components to prevent current overloading. Rather, it provides a closed, essentially zero-resistance circuit between a power source and the shorted circuit's wire. While one can connect the diagnostic tool to one of the shorted circuit's own circuit breakers, if the short pulls enough current to trip the circuit breaker, the short locating tool is rendered useless.
Other short locating tools are described in U.S. Pat. No. 6,252,409 B1 to Iijima; U.S. Pat. No. 5,877,631 to Takahashi; U.S. Pat. No. 5,476,497 to Mower et al.; U.S. Pat. No. 5,463,322 to Kwasnick et al. These are all complicated and potentially expensive devices, require significant expertise to use, or have very specific applications.
What is needed is an inexpensive but reusable simple-to-use short locating tool that provides protection for the electrical circuit being diagnosed without requiring replacement of fuses or resetting of circuit breakers. This is particularly needed for home appliance and HVAC service technicians.